We are improving CT colonography (virtual colonoscopy) by developing computer-assisted diagnosis methods. These methods attempt to identify and characterize colonic polyps automatically, thereby increasing physician accuracy and efficiency and helping patients by finding their polyps. We made a number of advances over the past year. We are developing techniques to identify the colon on CT scans using the marginal artery of the colon as a fiducial marker. We are working on a project to ascertain whether pericolonic visceral fat is a more useful predictive risk factor for colonic polyps compared with the more routinely used pan-abdominal visceral fat measurements. We are developing methods to detect extracolonic findings on CT colonography using fully-automated software.